Decade after decade, the Gallup Organization reported some of the most familiar numbers in American religion.
More than 90 percent of Americans said, "yes" when asked if they believe in God -- a number has changed little since the 1940s. Nearly 80 percent insisted they are "Christians," in some sense of that word. How many claimed to have attended a worship service in the previous week or so? That number hovered between 41 and 46 percent.

These are the kinds of numbers religious leaders love to quote when trying to intimidate politicians, educators, journalists and Hollywood producers.

"We revere the Bible, but don't read it," warned the famous pollster, in an address to the Evangelical Press Association. "We believe the Ten Commandments to be valid rules for living, although we can't name them. We believe in God, but this God is a totally affirming one, not a demanding one. He does not command our total allegiance. We have other gods before him."

The bottom line, he said, in an interview after that 1990 address, is that most American believers simply "want the fruits of religion, but not the obligations."

Gallup didn't enjoy punching holes in comforting statistics, in part because he sincerely believed that religious faith played a powerful, and for many decades overlooked, role in American life. This conviction was both professional and personal, since Gallup seriously considered becoming an Episcopal priest and earned a Bachelor of Arts degree in religion at Princeton University before joining the family business.

Thus, while his father forever linked the Gallup name with political polling, George Gallup Jr. added a new goal for the firm's research -- probing the links between religious life and public life. Gallup retired in 2004 and died on Nov. 21 at the age of 81, after a one-year battle with cancer.

The key to Gallup's legacy is that he built on the basic religious questions his father and other researchers included in polls during the 1940s and '50s, said political scientist John C. Green of the University of Akron, who is known for his research into American politics and religious life. Instead of merely asking questions about religious affiliations, Gallup advocated a more systematic approach that focused attention on religious beliefs, attitudes and even behaviors.

"You got the sense that, however valuable those general numbers were in earlier polls, he was showing that you could experiment and try to find the realities inside all those numbers," said Green. The earlier Gallup numbers were "valuable because some of them went back so far into the mid-20th century. Then, George Gallup Jr. showed everyone that you could go beyond that general approach and dedicate entire surveys to religious questions."

By the end of his career, it was common to see a variety of researchers -- at the Pew Forum, LifeWay Research, the Barna Group and elsewhere -- focusing their work on highly specialized surveys targeting religious issues and trends. In 1977, Gallup himself helped found the Princeton Religion Research Center, in part to produce materials that would help clergy be more effective.

The basic problem, Gallup told me in 2004, is that far too many clergy "simply fail to take discipleship seriously. They assume that because people say they believe something, that this means they will live out those beliefs in daily life."

This shows up in the building blocks of faith, he added. Many clergy, for example, assume that people in their flocks understand simple Bible references. Many assume that people in their pews understand the truth claims of other religions. Many clergy are naive enough to believe that postmodern believers will -- without being challenged -- confess their sins and change the behaviors that cause havoc in their lives.

"America is a churched nation, for the most part. Most Americans are either going to church or they used to go to church," said Gallup. "At some point we need to start focusing more attention on what is happening or not happening in those churches. ... Are our people learning the basics? Is their faith making a difference in their lives? Is their faith attractive to other people?